2 PETROLEUM AND PRODUCTION Petrolem Petra Oleum Rock Oil Petroleum is often called crude oil fossil fuel or oil It is called a fossil fuel because it was formed from the remains of tiny sea plants and animals that died millions of years ago ID: 571841
Download Presentation The PPT/PDF document "Bituminous Materials" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Bituminous MaterialsSlide2
2
PETROLEUM AND PRODUCTION
Petrolem = Petra + Oleum
Rock + Oil
Petroleum is often called
crude oil
, fossil fuel or oil.
It
is called a fossil fuel because it was formed from the remains of tiny sea plants and animals that died millions of years ago.
When
the plants and animals died, they sank to the bottom of the oceans.
Here
, they were buried by thousands of kms of sand and sediment, which turned into
sedimentary rock
.
As
the layers increased, they pressed harder and harder on the decayed remains at the
bottom.
The
heat and pressure changed the remains and, eventually, petroleum was formed. Slide3Slide4
How coal formed
Over millions of years, due to high temperatures and pressure…
the
trees became fossilized, forming coal.
Millions of years ago trees died and fell to the bottom of swamps.
Over time they became covered by mud and rock.Slide5
How oil and natural gas formedSlide6
6Slide7Slide8
Where We Get Oil?
The world's top five crude oil-producing countries are:
Saudi Arabia
Russia United States Iran China Slide9
Concentration of Oil
Structural Traps
Fault
Anticline
Salt dome
http://www.priweb.org/ed/pgws/systems/traps/traps_home.htmlSlide10
Concentration
of OilSlide11
Concentration
of OilSlide12
12
Boiling
point
Density
Odour
Viscosity
Light-heavy : Low boiling point and relative density
Heavy-heavy : High boiling point, viscous.
Because crude oil has Fe, Mg,
Ca
, P, V, S, Zn, Co, clay, water and
other residuals
, it has to distillate for internal combustion engines.
Petroleum is defined by 4 physical categories historicallySlide13
13
1
World
85.220.000
2
United States
20.680.000
3
European Union
14.380.000
4
China
7.880.000
5
Japan
5.007.000
6
India
2.722.000
7
Russia
2.699.000
8
Germany
2.456.000
9
Brazil
2.372.000
10
Canada
2.371.000
11
Mexico
2.119.000
12
Korea, South2.080.00013France1.950.000
14United Kingdom1.763.00015Italy1.702.00016Spain1.611.00017Iran1.600.00018Indonesia1.564.00019Saudi Arabia1.000.00020Netherlands984.20026Turkey676.600
2009 Oil consumption bbl/daySlide14
Crude oil is a
mixture
.
It contains hundreds of different compounds.
Some
are small but most are large.
Nearly all of these compounds contain carbon and hydrogen
only.
They are called hydrocarbons.
Also some other compounds contain small amounts of N and S. Why?
Hydrocarbons are molecules that contain carbon and hydrogen
only
.
Crude OilSlide15
15
Element
Percent range
Carbon
83 to 87%
Hydrogen
10 to 14%
Nitrogen
0.1 to 2%
Oxygen
0.05 to 1.5%
Sulfur
0.05 to 6.0%
Metals
< 0.1%
Composition by weight
Hydrocarbon
Average
Range
Paraffins
30%
15 to 60%
Naphthenes
49%
30 to 60%
Aromatics
15%
3 to 30%
Asphaltics
6%
remainderSlide16
Oil
Refining
Typical Oil
Gasoline C4 to C10 27%
Kerosene C
11
to C
13
13%Diesel C14 to C18
12%Heavy gas oil C19 to C25 10%Lubricating oil C26-C40 20%Residue >C40 18%Slide17
The hydrocarbons in crude oil are essential to our way of life
We use them as fuels for most forms of transport.
We also use them as raw materials from which a
HUGE range of useful everyday substances are made
The importance of oilSlide18
Crude oil is a mixture of hydrocarbons with a VERY wide range of sizes.
Crude oil itself has no uses because its properties
are not
definite. To make crude oil into useful substances we have to separate the mixture into molecules of similar size.This is done in an
oil refinery
in a process called fractional distillation.
The physical property used to separate the fractions is boiling point.
Making Oil UsefulSlide19
19
Oil
drilling occurs both at sea and on land, depending on the size and profitability of the oil deposits located.
The first step is the transport of the crude oil from its natural location to the refinery.
Once obtained from the ground, the oil is transported by ship, truck or pipeline to the refinery.
From the Field to the Refinery
Extraction process of crude oil from the SeaSlide20
Oil Rig from airSlide21
21
To
separate it into useful products begins.
Have complex stages and each part have several processes.
The very first step is to break up the crude oil.
Fractional Distillation Of Crude OilSlide22
Distillation
Distillation separates chemicals by the difference in how easily they vaporize.
The
two major types of classical distillation include continuous distillation and batch distillation.Continuous distillation, as the name says, continuously takes a feed and separates it into two or more products.
Batch
distillation takes on lot (or batch) at a time of feed and splits it into products by selectively removing the more volatile fractions over time
.
Many industries use distillation for critical separations in making useful products. These industries include petroleum refining, beverages, chemical processing, petrochemicals, and natural gas processing.Slide23
23
Fractional distillation of crude oil is the first step in the production of
many
of
the materials we have come to rely on in modern life.
All our fossil fuels, virtually all our plastics, detergents and commercial
alcohols
are
made from products of this process.In order to separate the different length chains in the crude mix, it is heated to
a very high temperature. The temperature cannot be set higher than this as there is a risk that the lighter
fractions will ignite.
Fractional Distillation Of Crude OilSlide24
24
Distillation is the most common form of separation technology used in petroleum refineries, petrochemical and chemical plants, natural gas processing
.
Industrial distillation is typically performed in large, vertical cylindrical
columns
known
as "
distillation or fractionation towers
" or "distillation columns"
with diameters
ranging from about 65 centimetres to 6 metres and heights ranging from about 6 metres to 60 metres or more.
The distillation towers have liquid outlets at intervals up the column which allow for the withdrawal of different
fractions or products having different boiling points or boiling ranges. By increasing the temperature of the product inside the
columns, the different hydrocarbons are separated.
The
"lightest" products
(those with the lowest boiling point) exit from the top of the columns and the
"heaviest" products (those with the highest boiling point) exit from the bottom of
the column
.
Fractional Distillation Of Crude OilSlide25
25
Industrial
Distillation Of Crude OilSlide26
Fractional DistillationSlide27
27
Major products of oil refineries
Liquid
petroleum gas (LPG)
Gasoline
(also known as petrol)
Naphtha
Kerosene
and related jet aircraft fuels
Diesel
fuel
Fuel
oilsLubricating oilsAsphalt and TarPetroleum
cokeSlide28
28
Fractional distillation is used in oil refineries to separate crude oil into useful
substances (or fractions) having different hydrocarbons of different boiling points
Major products of oil refineriesSlide29
29
Major products of oil refineriesSlide30
30
Major products of oil refineriesSlide31
31
Major products of oil refineriesSlide32
32
Asphalt
The products refined from the liquid fractions of crude oil
can be placed into ten main categories
Asphalt
Asphalt
is commonly used to make roads.
It
is a colloid of asphaltenes and maltenes that is separated from the other components of crude oil by fractional distillation.
Once
asphalt is collected, it is processed in a de-asphalting unit, and then goes through a process called “blowing” where it is reacted with oxygen to make it harden.
Asphalt
is usually stored and transported at around 150 C.Slide33
33
Diesel
Diesel is any fuel that can be used in a diesel engine.
Diesel
is produced by fractional distillation between 250° Fahrenheit and 350° Fahrenheit.
Diesel
has a higher density than gasoline and is simpler to refine from crude oil.
It
is most commonly used in transportation.
Fuel Oil
Fuel oil is any liquid petroleum product that is burned in a furnace to generate heat.
Fuel oil is also the heaviest commercial fuel that is produced from crude oil.
Diesel and Fuel OilSlide34
34
GASOLINE
Gasoline is an extremely flammable fuel source for automobiles and other vehicles and equipment.
A liquid, it can be colorless, pale brown or pale pink.
Gasoline is not a single substance.
There is no such thing as pure gasoline.
Gasoline is produced by refining petroleum, and it consists of a complex mixture of over 120 hydrocarbons. Slide35
35
Gasoline
It is mainly used as fuel in internal combustion engines, like the engines in cars.
Gasoline
is a mixture of paraffins, naphthenes, and olefins, although the specific ratios of these parts depends on the refinery where the crude oil is processed.
Gasoline
refined beyond fractional distillation is often enhanced with iso-octane and ethanol so that it is usable in cars.
Gasoline is called different things in different parts of the world.
Some
of these names are: petrol, petroleum spirit, gas, petrogasoline, and mogas.
Kerosene
Kerosene is collected through fractional distillation at temperatures between 150° Fahrenheit and 275° Fahrenheit. It is a combustible liquid that is thin and clear.
Kerosene is most commonly used as jet fuel and as heating fuel.
Gasoline and KeroseneSlide36
36
Liquefied Petroleum Gas
Liquefied petroleum gas is a mixture of gases that are most often used in heating appliances, aerosol propellants, and refrigerants.
Different
kinds of liquefied petroleum gas, or LPG, are propane and butane.
At
normal atmospheric pressure, liquefied petroleum gas will evaporate, so it needs to be contained in pressurized steel bottles.
Lubricating
Oil
Lubricating oils consist of base oils and additives.
Different lubricating oils are classified as paraffinic, naphthenic, or aromatic. Lubricating oils are used between two surfaces to reduce friction and wear. The most commonly-known lubricating oil is motor oil, which protects moving parts inside an internal combustion engine.
Liquefied Petroleum
Gas and KeroseneSlide37
37
Paraffin Wax
Paraffin
wax is a white, odorless, tasteless, waxy solid at room temperature.
The
melting point of paraffin wax is between 47° C and 65° C, depending on other factors.
It
is an excellent electrical insulator, second only to Teflon®, a specialized product of petroleum.
Paraffin
wax is used in drywall to insulate buildings. It is also an acceptable wax used to make candles.Bitumen
Bitumen, commonly known as tar, is a thick, black, sticky material. Refined bitumen is the bottom fraction obtained by the fractional distillation of crude oil.
This means that the boiling point of bitumen is very high, so it does not rise in the distillation chamber. The boiling point of bitumen is 525° C. Bitumen is used in paving roads and waterproofing roofs and boats. Bitumen is also made into thin plates and used to sound proof dish
washers and hard drives in computers.
Paraffin Wax and BitumenSlide38
Why do these fractions condense over a boiling
range?
Fraction
Boiling Range (
o
C)
Fuel gas
Below 40
Petrol
40 - 175
Kerosene
150 - 240
Diesel
220 – 275
Lubricating oil
250-350
Bitumen
>350
cool
hot
Fuel gas
Petroleum
Kerosene
Diesel
Lub. Oil
Bitumen
Fractional DistillationSlide39
Fuel gas
Petrol
/ gasoline
Naphtha
Paraffin /
Kerosine
Diesel fuel
Fuel and
lubricating
oil
Bitumen
Burned in the refinery to fuel the distillation process, sold as LPG, purified and sold as
bottled camping gas
Fuel for cars
and motorcycles, also used to make chemicals.
Used to
make chemicals used
everwhere
.
Fuel for
green house
heaters and
jet engines
, manufacture of chemicals.
Fuel for
lorries
and
trains.
Fuel for the heating systems of large buildings, fuel for ships,
lubricating oil
.
Roofing, and
road surfaces
.
Uses of each fractionSlide40
In general, the bigger the molecule the higher the boiling point.
No. Carbon atoms
B.Pt
(
o
C)
The boiling points of moleculesSlide41
Here are the boiling ranges of some fractions obtained from distillation of petroleum
.
Fraction
Boiling Range
(
o
C)
Number of carbons
Fuel gas
Below 40
Petrol
40 - 175
Kerosine
150 - 240
Diesel
220 - 275
1-5
5-10
9-14
13-17
boiling rangesSlide42
What is Bitumen?
In North America, bitumen is commonly known as “asphalt cement” or “asphalt binder.”
Asphalt pavement is a mixture of about 5 percent bitumen (asphalt cement) and 95 percent small stones, sand, and gravel.
Bitumen (asphalt cement) is produced by distillation of crude oil during petroleum refining. It also occurs naturally.Bitumen can be divided into broad categories based on physical properties and specifications for different uses.
Straight-run bitumen is used in paving
Oxidized bitumen is used in roofing
42Slide43
Coal is a fossil fuel mined from ancient deposits.
It is a black mineral of plant origin which is chemically, a complex mixture of elemental carbon, compounds of carbon containing hydrogen, oxygen, nitrogen and
sulphur
.Coal is believed to have been formed about 300 million years ago under the Earth by a process called carbonization.Carbonization is the process of slow conversion of vegetable matter to coal under the Earth due to the action of high pressure, high temperature, anaerobic bacteria and absence of oxygen.
What is Coal Tar? Slide44
Formation of coal in flow diagramSlide45
Types of coal
Depending upon the extent of carbonization, coal can be classified into four types as follows:
Classification of coal
Peat 11% ,
Lignite 38% (Soft coal / brown coal)
Bituminous 65% (Household coal)
Anthracite 96% (Hard coal)
Peat is the first stage in the conversion of vegetable matter to coal while anthracite is the last.Slide46
Distillation or Destructive distillation of coal ?
The process of heating coal in the absence of oxygen to obtain useful products is called destructive distillation of coalSlide47
Product
Formed/collected in
Uses
Coal Tar (complex mixture of carbon compounds)
Bottom of the test tube B. Liquid residue insoluble in water
Can be distilled to obtain: Benzene — solvent Toluene — manufacture of explosive TNT Naphthalene — insect repellent
Coal gas (CH
4
+CO+H
2
)
Combustible gas insoluble in water. Escapes through the side tube
Industrial fuel Liquor ammonia (NH4OH)
Soluble in water present in test tube Manufacture of nitrogenous fertilizers Coke (98%C)
Solid residue left behind in test tube A
i
) Reducing agent in metallurgy
ii) Manufacture of water gas and producer gas — Industrial fuel
Products formed and their uses
Slide48
48
Comparison between Asphalt and Tar
SIMILARITIES:
Composed
principally of Bitumen.
Black
or dark brown in color.
Cementitious
.
Water
repellent.DIFFERENCES:
Distinguished by odor (tar has an aromatic odor).The
insoluble portion in natural asphalt is mineral matter, while the insoluble in tar is free carbon.
Tar molecules tend to be aromatic (ring or cyclic), while asphalt molecules tend to be aliphatic (straight chain)
Tar is more temperature
susceptible
Tar can coat aggregates better and
is more
water resistant
.
Asphalt is more weather
resistant.
Asphalt can occur in natural form
or come
as a by-product of
petroleum refinery
. Tar does not occur in
natural form
, but comes as a by-product in
the manufacture
of coke or water-gas
.
Fumes from heated tar cause
health hazards
such as severe eye and
skin irritation.Slide49
49
Bituminous
Tar
Comparison between Asphalt and TarSlide50
50
The composition of bitumen
Bitumen is a complex combination of hydrocarbons with small quantities
of
sulphur
, oxygen, nitrogen and trace quantities of metals such as vanadium
, nickel
, iron, magnesium and calcium.
Crude
oils normally contain
small quantities of polycyclic aromatic hydrocarbons (PAHs), a portion of which end up in bitumen.
Although some of these PAHs are suspected of causing cancer in humans, the concentrations are extremely low and no causal link to cancer in humans has been established.
Most bitumens manufactured from a range of crude oils contain:
Carbon 82 - 88%Hydrogen 8 - 11%Sulphur 0
- 6%
Oxygen
0
- 1.5%
Nitrogen
0
- 1%Slide51
51
Broad chemical components of bitumen
It is convenient to
separate bitumen
into two broad chemical groups, called
asphaltenes
and
maltenes
Maltenes
are further subdivided into saturates, aromatics and resinsSlide52
52
Asphaltenes
Asphaltenes are fairly high molecular weight, n-heptane insoluble
solids that
are black and glassy.
They
make up 5 - 25% of the bitumen,
and contain
carbon, hydrogen, some nitrogen,
sulphur
and oxygen. The asphaltenes
content has a significant influence on the rheological properties of the bitumen. Increasing the
asphaltenes content produces a harder, more viscous binder.Slide53
53
Resins
Resins are largely composed of hydrogen and carbon, with small
amounts of
oxygen,
sulphur
and nitrogen, making up 30 - 50% of the total bitumen.
These dark brown solids or semi-solids act as a dispersing (
peptising
) agent
for the asphaltenes. Being polar in nature, they are
strongly adhesive. The properties of resins characterise
to a degree the type of bitumen, i.e. "solution" (SOL) or "gelatinous" (GEL) (see Bitumen structure.)Slide54
54
Aromatics
Aromatics are dark brown, low molecular weight, viscous fluids making
up 40
- 65% of the total bitumen, and the ability to dissolve other,
high molecular
weight hydrocarbons.
The
aromatic content of the
bitumen determines
to a significant extent its compatibility with polymers used for modification.Slide55
55
Saturates
Saturates are straw
coloured
or white, viscous oils with a molecular
weight similar
to that of aromatics.
They
contain both waxy and
non-waxy saturates
and make up 5 - 20% of the bitumen.Slide56
A
fluid is defined as a material which will continue to deform with the application of a shear force. However, different fluids deform at different rates when the same shear stress (force/area) is applied.
Viscosity is that property of a real fluid by virtue of which it offers resistance to shear force.
For a given fluid the force required varies directly as the rate of deformation. As the rate of deformation increases the force required also increases.
The force required to cause the same rate of movement depends on the nature of the fluid.
The resistance offered for the same rate of deformation varies directly as the viscosity of the fluid.
As viscosity increases the force required to cause the same rate of deformation increases.
Viscosity of FluidsSlide57
h
L
Force
Area
Viscosity of FluidsSlide58
Dynamic Viscosity
1
centi
-Poise =
milli
Pascal-second
SI Unit: Pascal-second
Shear stress
Shear rate
Newton’s law of viscosity states that the shear force to be applied for a deformation rate of (
du
/
dy
) over an area A is given by,
where
F
is the applied force in N,
A
is area in m
2
,
du
/
dy
is the velocity gradient (or rate of deformation), 1/s, perpendicular to flow direction, here assumed linear, and μ is the proportionality constant defined as the
dynamic or absolute viscosity
of the fluid.Slide59
Dynamic Viscosity
The dimensions for dynamic viscosity μ can be obtained from the definition as Ns/m
2
or kg/
ms.
The
first dimension set is more advantageously used in engineering problems.
However
, if the dimension of N is substituted, then the second dimension set, more popularly used by scientists can be obtained.
The
numerical value in both cases will be the same.
N = kg m/s2 ; μ = (kg m/s2) (s/m2) = kg/m/s
The popular unit for viscosity is Poise named in
honour
Poise = 0.1 Ns/m
2
Centipoise (
cP
) is also used more frequently as,
cP
= 0.001 Ns/m
2Slide60
Kinematic Viscosity
The ratio of dynamic viscosity to the density is defined as kinematic viscosity, ν, having a dimension of m
2
/s.
Later it will be seen to relate to momentum transfer.
Because of this kinematic viscosity is also called momentum diffusivity.
The popular unit used is stokes (in
honour
of the scientist Stokes).
Centistoke is also often used.
1 stoke = 1 cm
2
/s = 10–4
m2/sof all the fluid properties, viscosity plays a very important role in fluid flow problems.The velocity distribution in flow, the flow resistance etc. are directly controlled by viscosity.Slide61
Typical Viscosities (
Pa
.
s
)
Asphalt Binder ---------------
Polymer Melt -----------------
Molasses ----------------------
Liquid Honey -----------------
Glycerol -----------------------
Olive Oil -----------------------
Water --------------------------
Acetic Acid --------------------
100,000
1,000
100
10
1
0.01
0.001
0.00001
Courtesy: TA InstrumentsSlide62
Newtonian
Fluids
Shear stress
Shear rate
Examples:
Water
Milk
Vegetable oils
Fruit juices
Sugar and salt solutions
Fluids of the most commonly encountered in fluid engineering are water and air, and also, include structurally simple fluids with low molecular weight, are found to obey “Newton’s law of viscosity”.
Such fluids are referred to as Newtonian fluids.
The Newton’s law of viscosity states that the shearing force is proportional to the shear ratesSlide63
Different types of Fluids
Shear stress
Shear
rate
Newtonian
Pseudoplastic
(or Shear thinning)
Dilatant (or Shear thickening)
Bingham Plastic
Casson Plastic
Non Newtonian FluidsSlide64
Non-Newtonian Foods
In a general sense, fluids that exhibit characters not predicted by the Newtonian constitutive equation (linear) are non-Newtonian.
The exceptions to the Newtonian fluids are not of rare occurrence, and in fact many common fluids are non-Newtonian.
Some examples are: paints, solutions of various polymers and molten plastics; food products such as apple sauce, ketchup and other mammalian whole foods; synovial fluid found in joints, blood and other organic fluids; many solid-liquid and liquid-liquid suspensions such as
fibers
in a liquid paper pulp, coal slurries, emulsions of water in oil or oil in water, and so on.
The so-called non-Newtonian fluids, as mentioned above, are often found in many fields of engineering fluid mechanics as well as in bio-medical fields, and exhibit interesting, useful and even exciting characteristics differed from those found in Newtonian fluids.Slide65
65
Bitumen Structures
The molecules in the bitumen further fall into two
functional categories
- polar and non-polar molecules:
Polar
molecules form the network of the bitumen and provide
the elastic
properties;
Non-polar
molecules provide the body of the bitumen and its viscous properties.These two categories of molecules co-exist, forming a
homogeneous mixture. Their weak interaction results in the Newtonian behaviour
of bitumen at high temperatures, where the viscosity change is directly proportional to the temperature change.Slide66
66
"solution" type (SOL) bitumen
In the presence of sufficient quantities of resins and aromatics of
adequate solvating
capacity, the
asphaltenes
are fully dispersed, or
peptised
, and
the resulting
micelles have good mobility within the bitumen. In such cases the bitumen is known as a "solution" type (SOL) bitumen as shown in Figure 6.Slide67
67
"solution" type (SOL) bitumen
If the aromatic or resin fraction is not present in sufficient quantities
to
peptise
the micelles, or has insufficient solvating capacity, the micelles
can associate
together.
This
leads to structures of linked micelles, and these types of bitumen are known as "gelatinous" (GEL) types and are depicted in the Figure.Slide68
68
Temperature
Bitumen is a thermoplastic hydrocarbon material which softens
when heated
and turns into a glassy state when cooled.
The
following
states generally
describe the consistency of bitumen at various temperatures:
At low road temperatures - a brittle solid;
At room temperature - a sticky semi-solid;
At high service temperatures - a viscoelastic1 substance;
At elevated temperatures - a viscous liquid.Slide69
69
Viscoelastic properties
Bitumen displays both elastic and viscous
behaviour
, depending largely
on temperature
and load duration.
This
viscoelastic character of
bitumen results
in its varied response behaviour under varied loading times and temperatures
changes.Elastic behaviorAt low temperature and short duration loads:
Bitumen tends to act as an elastic solid, returning to its originalposition after removal of the load;
Excessively low temperature in conjunction with rapid loading may cause brittle failure and cracking;Prolonged low temperature can cause a build-up of internal stress resulting
in cracking.Slide70
70
Viscoelastic properties
Bitumen displays both elastic and viscous
behaviour
, depending largely
on temperature
and load duration.
This
viscoelastic character of
bitumen results
in its varied response behaviour under varied loading times and temperatures
changes.
Viscous behaviorAt elevated temperature and long duration loads:
Bitumen acts as a viscous fluid - i.e. it undergoes plastic deformation that is not recoveredFlow takes place as adjacent molecules flow past each
other
The
force resisting this flow is related to the relative velocity of
slidingSlide71
Many materials display time dependence in their elastic response
gum
bread dough
cheeseViscoelastic materials possess both elastic and flow characteristicsViscoelastic propertiesSlide72
Viscoelastic propertiesSlide73
Consider a material placed under a weight. A constant stress is applied, and we measure how the strain (∆h/h) changes with time
O
r
i
g
i
n
a
l
h
F
C
o
m
p
r
e
s
s
e
d
∆
h
Elastic MaterialSlide74
Elastic Material
O
r
i
g
i
n
a
l
h
F
C
o
m
p
r
e
s
s
e
d
∆
h
∆h
Time
Instantaneous
elastic
deformation
Instantaneous
elastic
recovery
force applied
force removed
Elastic MaterialSlide75
O
r
i
g
i
n
a
l
h
F
C
o
m
p
r
e
s
s
e
d
∆
h
Instantaneous
elastic
deformation
∆h
Time
force applied
force removed
retarded
deformation
(creep)
Instantaneous
elastic
recoveryretardedrecoverypermanent deformationViscoelastic MaterialSlide76
Viscoelastic Material
Unlike purely elastic substances, a viscoelastic substance has an elastic component and a viscous component.
The
viscosity
of a viscoelastic substance gives the substance a strain rate dependent on
time.
Purely
elastic materials do not dissipate energy (heat) when a load is applied, then removed
.However, a viscoelastic substance loses energy when a load is applied, then removed.
Hysteresis is observed in the stress-strain curve, with the area of the loop being equal to the energy lost during the loading cycle.
Since viscosity is the resistance to thermally activated plastic deformation, a viscous material will lose energy through a loading cycle.
Plastic deformation results in lost energy, which is uncharacteristic of a purely elastic material's reaction to a loading cycle.Specifically, viscoelasticity is a molecular rearrangement.
When
a stress is applied to a viscoelastic material such as a
polymer
, parts of the long polymer chain change position. Slide77
Rheology of BitumenSlide78
What is Rheology of Bitumen?
Study of
flow
and
deformation
behavior of Bitumen
Rheology
is the science of the flow and deformation of fluids
and constitutes
a fundamental engineering property of bitumen. The
rheological properties
of bitumen are influenced by both its temperature and chemical composition
and the structure - or physical arrangement - of the molecules Slide79
Elastic ResponseSlide80
Viscous ResponseSlide81
Maxwell ModelSlide82
Kelvin-Voigt ModelSlide83
Combination of Maxwell and Kelvin-VoigtSlide84
84
Burger’s Model
Burger's model is often used to
characterize
the response of bitumen
to imposed
stresses.
A spring and dashpot in series (Maxwell model);
o
Spring and dashpot in parallel (Kelvin-Voigt model).Slide85
85
Burger’s ModelSlide86
Burgers ModelSlide87
Low temperature and short duration loading
At low temperatures and/or high frequency (short duration) loads,
bitumen tends
to act as an elastic solid, returning to its original position after removal of the load.
This
almost purely elastic
behavior
can be represented by a simplified Burger's model as a spring in series with the Kelvin-Voigt
model or
even a spring only
.Excessively low temperatures in conjunction with rapid loading may cause brittle failure and cracking. Prolonged low temperatures can also cause
a build-up of internal stresses in the bitumen, resulting in cracking as it interacts with the rest of the pavement structure.Slide88
High temperature and long duration loading
At elevated temperatures and/or low frequency (prolonged duration) loads
, bitumen
acts as a viscous fluid.
It
will undergo plastic deformation i.e.
the deformation
is not reversible.
Flow
takes place as adjacent molecules
slide past each other, the resulting friction or resistive force being related to the relative velocity of sliding.
The relationship of this resistive force and the relative velocity (of sliding) is termed "viscosity".
Under conditions of elevated temperature, pavements bound with bitumen will tend to rut under repeated applications of wheel loads, and the rutting will occur at a rate dependent on the temperature and rate of loading.
This plastic behavior of the bitumen at high temperatures can be offset by the interlocking action of the aggregate, which serves to resist permanent deformation.Slide89
Intermediate temperature
behavior
At intermediate temperatures bitumen displays both elastic and
viscous
behaviour
as represented in the Burger's model.
After
an instantaneous
elastic response
, a gradual increase in strain with time takes place until the load is removed.
The change in strain with time is caused by the viscous behaviour of the material.
On removal of the load, the elastic strain is recovered instantaneously and some additional recovery occurs with time
- known as delayed elasticity. Ultimately a permanent residual strain remains, i.e. rutting, which is irrecoverable and is directly caused by
viscous
behaviour
.Slide90
90
Response of asphalt in a simple creep testSlide91
91
Advantages of the
viscoelastic
behaviour of bitumen
The most common state of bitumen is viscoelastic, enabling it
to exhibit
the advantageous properties of both elastic and
plastic materials
;
As
a binder it provides excellent adhesive properties with mineral aggregates;Bitumen
acts as a lubricant when heated, thereby facilitating spraying, coating of aggregates during hot mix manufacture, as well as compaction during laying;
Bitumen cools to become a glue, forming part of the solid matrix.With a binder well-matched to the loading and temperature conditions, the most common response is elastic or viscoelastic, with only
a limited plastic behavior.Slide92
92
Cutback Bitumen
Cutback bitumen is a blend of penetration grade bitumen and petroleum
solvents.
The
choice of solvent determines the rate at which the bitumen
will "set up" or cure when exposed to air.
A
rapid-curing (RC) solvent
will evaporate
more quickly than a medium-curing (MC) solvent.
The viscosity of the cutback bitumen is determined by the proportion of solvent added - the higher the proportion of solvent, the lower is the viscosity of the cutback.
The solvent used in cutback bitumen is sometimes also referred to as the "cutter" or "flux".
When the solvent has evaporated, the binder reverts to the original penetration grade. The advantage of cutback bitumen is that it can
be applied
at lower temperatures than penetration grades because of its
lower Bitumen Solvents viscosity
. A disadvantage is that cutback bitumen consumes non
renewable energy
resources which are ultimately lost through evaporation.Slide93
Creep
: deformation that occurs over period of time when a material is subjected to a constant stress (at constant temperature)
CreepSlide94
Slide95
Elastic Material
: stress increases immediately with strain and remains constant
Newtonian Fluid
: stresses increases with application of strain, quickly declines to zero
Viscoelastic material
: stress increases immediately, declines gradually over time.
viscoelatic
solid-decline is gradual and levels off at
e
viscoelatic liquid, stress declines rapidly and goes to zeroSlide96Slide97Slide98
98
To illustrate how viscoelastic materials respond to applied loads it
is common
practice to represent material behaviour
by a system of springs
to simulate
the elastic components, and dashpots to simulate the
viscous
behaviour
as follows:Spring:o
Elastic deformation;o Not time dependent;o No permanent deformation.
• Dashpot:o Viscous deformation;o Time dependent;
o Some permanent deformation.• Spring-dashpot in parallel Delayed elastic deformation;
Time
dependent;
o
No permanent deformation.Slide99
Elastic ResponseSlide100
Viscous ResponseSlide101
Maxwell ModelSlide102
Bitumen plays a vital role in road construction typically as binder.
Application condition requires bitumen to behave as mobile liquid.
There are three ways to reduce its viscosity:
Heat it
Dissolve it in solvents
Emulsify it.
In heating it involves some:
Energetic
Environmental and
Health problems
As process is inefficient and involves
Loss of heat and even fumes causing
air pollution
102
In case using solvents:
We make use of volatile dilatants like kerosene petroleum which adds to its
cost although
viscosity
get
reduced as it is uneconomical.Slide103
103
Types and grades of bituminous binders
Penetration grade bitumen
Penetration grade bitumen can be manufactured by
straight-run distillation or
by blending two base components (one hard such as 35/50 pen and
the other
soft such as 150/200 pen).
Penetration
grade bitumen is used either as a primary binder or base bitumen for the manufacture of:
Cutback bitumen;Modified binders;Bitumen emulsions.Slide104
104
Cutback Bitumen
Cutback bitumen is a blend of penetration grade bitumen and petroleum
solvents.
The
choice of solvent determines the rate at which the bitumen
will "set up" or cure when exposed to air.
A
rapid-curing (RC) solvent
will evaporate
more quickly than a medium-curing (MC) solvent.
The viscosity of the cutback bitumen is determined by the proportion of solvent added - the higher the proportion of solvent, the lower is the viscosity of the cutback.
The solvent used in cutback bitumen is sometimes also referred to as the "cutter" or "flux".Slide105
105
Polymer modified bitumen
The rheological properties of conventional binders may be modified by
the introduction of
:
Elastomers
;
Plastomers
;
Crumb rubber;
Hydrocarbons.Modification is costly and is normally justified when bituminous
surfacings are subjected to severe conditions such as:Steep gradients;
Very high road surface temperature;High traffic loading; or
Heavily trafficked intersections.Modification may also be advantageous for surfacings on highly flexible and cracked pavements, where an improvement in the rheological properties
of the
bitumen is required.
Use
in such applications should be guided
by expert
opinion.Slide106
106
Polymer modified bitumen
In addition to the primary aims above, the range of properties improved include
Durability;
Aggregate
retention;
Resistance
to permanent deformation;
Resistance
to fatigue cracking;
Cohesion (internal strength);
Elasticity;Viscosity less susceptible to temperature changes.Modification agentsSlide107
107
Polymer modified bitumen
The primary aim of the modification of bitumen for use in structural layers
is to increase the resistance of these layers to permanent deformation at
high road
temperatures without compromising the properties of these
layers over
the rest of the prevailing temperature range.
The use of polymer modified bitumen to obtain improved performance
is rising
as a result of increases in tyre pressures, axle loads and higher traffic volumes.
Improved performance can be achieved in two ways, both of which are aimed at reducing the permanent strain:An
increase in the elastic component with an associated reduction in the viscous component; andStiffening of the bitumen to reduce the total viscoelastic response of the
layer.Slide108
108
Polymer modified bitumen
Modification is achieved by the introduction of polymers (including
crumb rubber
), aliphatic synthetic wax or naturally occurring hydrocarbons.
Polymers can be broadly
categorized
as "elastomers" (sometimes
referred to
as thermoplastic elastomers) for improving the strength and
elastic properties of a binder, and "plastomers" (sometimes referred to asthermoplastic polymers) for increasing the viscosity of the bitumen.Slide109
109
Types and varieties of ModifiersSlide110
110
Bitumen Additives
A number of bitumen additives are employed, particularly in asphalt.
These additives are not intended to modify or improve the rheological properties
of bitumen
; rather the intention is to improve certain
performance characteristics
to extend the service life of the asphalt.Slide111
What are emulsions?
111Slide112
Types of emulsions:
(a) O/W emulsion,
(b) W/O emulsion, (c) multiple W/O/W.
112Slide113
BITUMEN EMULSION
Bitumen Emulsion is a 2-phase system consisting of
Bitumen
Water
Other Additives
The bitumen is dispersed throughout the water phase in form of
discrete globules
,
held in
suspension by electrostatic charges stabilized by emulsifier
The Emulsion contains 40-75% of bitumen,.1-2.5
% emulsifier, 25-60% water
and
other ingredients Typically
of
0.1
– 50 µm in diameter.
It is mainly dark brown in color after breaking changes to black.
113Slide114
114
WHY BITUMEN EMULSIONS ?
Primary
objective is to use for road surfacing without much heating.
As main advantages this improves the handling of bitumen at room temperature.
Promotes surface interactions .
Its mixture with the aggregate attains full strength.
Economical and saves energy
.
Reduced atmosphere pollution.
Water can also added before use to dilute as per requirement.
Rains can not effect it at the time of use and after use.Slide115
Types
Bitumen emulsions can be divided into four classes:
Cationic emulsions.
Anionic emulsions.
Non-ionic emulsions.
Clay-stabilized emulsions.
The first two are most widely used
115Slide116
Cationic emulsions
If an electric potential is supplied between two electrodes immersed in an emulsion containing positively charged particles of bitumen, they will migrate to the cathode.
This emulsion is said to be cationic.
116Slide117
Anionic emulsions
If an electric potential is supplied between two electrodes immersed in an emulsion containing negatively charged particles of bitumen, they will migrate to the anode.
This
emulsion is said to be anionic.
117Slide118
Non-ionic emulsions
If the bitumen particles in the emulsion are neutral, then they will not migrate to any of the pole.
These type of emulsions are NON-IONIC.
Mainly used in road ways.
118Slide119
Clay-stabilized emulsions
These are mainly used for industrial applications.
In these materials, emulsifiers are fine powders, often natural or processed clays and
bentonites.Particle size is very much less when compared with the bitumen particles in emulsions.
119Slide120
120Slide121
Manufacture of Bitumen emulsions
Bitumen emulsions can be manufactured using batch process or continuous process.
Bitumen emulsions are made in continuous inline processes involving dispersing technologies like rotor stators, colloidal mills and static mixers.
High shearing forces are required for producing emulsions.
Colloidal mills contain high speed rotors.
Hot bitumen and emulsifier are fed simultaneously into colloidal mill.
121Slide122
Manufacturing conditions
The speed of rotors is in the range of 1000-6000 revs/min.
Bitumen is generally heated to temperature of 100-140 degree
Celsius.The viscosity of the bitumen is kept less than 2 poise.
122Slide123
123
Figure 2. Schematic diagram of a bitumen emulsion plantSlide124
124Slide125
125
As an alternative to colloid mill, a static mixer can be used.
This contains no moving parts.
The high shear necessary to produce an emulsion is generated by pumping the input materials at high speed. Slide126
Properties of bitumen emulsion
It is stable under transportation ,storage & application condition.
But it may break soon after application.
It may have low viscosity
It may flow due to irregular spraying but not due to road irregularities
Important properties of Bitumen emulsion:
Stability
Viscosity
Breaking
Adhesivity
126Slide127
Emulsion stability
This property indicates the resistance ability to change properties over time.
As stability is very important in storage , transport & use.
Stable emulsion will change over time slowly.
Reason for instability can be physical or chemical process.
As emulsion is a example of colloidal system in non equilibrium state.
Emulsion will go through several process like fl
occulation, sedimentation, and coalescence leading to instability of emulsion
127Slide128
Emulsion Viscosity
The viscosity of the bitumen emulsion is important for pumping and transportation.
In some applications, for example surface dressing, bitumen emulsion is sprayed on the road.
In this case the viscosity is critical. As it
should be low enough to permit even spraying but at the same time high enough to prevent run-off, once it is sprayed on the road.
128Slide129
Emulsion breaking
Bituminous emulsions are designed to “break” deliberately in contact with moist aggregates, releasing a binder film on and between the mineral aggregates.
There can be two kind of breaking:
Breaking of anionic bitumen emulsions
Breaking of cationic bitumen emulsions
129Slide130
Uses of Bitumen emulsion
Crack Filling:
To stop entering water in structural layer of pavement Bitumen emulsions preferably containing rubber are used as they are inexpensive and effective.
130Slide131
131
Grouting:
It is the method of construction or stabilizing of road surfaces and footpath. Emulsion is applied to compacted dry aggregate and due its low viscosity it penetrates through void structure of the aggregate.Slide132
Soil Stabilization:
For agricultural land where fresh top soil is susceptible to surface erosion ,bitumen emulsion can be used as binding agent also helps in retaining soil moisture & improving thermal insulation
Slip layer & concrete curing: Bitumen emulsions are used to create a membrane between layers of concrete to retain strength of upper layer by preventing water seepage into lower layers by avoiding rigid adhesion. Also it is sprayed on top surface to avoid evaporation of water.
132